An electric vehicle and plug-in hybrid vehicle include an inverter device for performing motor drive with the use of a high voltage storage battery for power drive and a low voltage storage battery for operating auxiliaries such as lights of the vehicles and a radio. Such a vehicle includes a DC-DC converter apparatus for performing power conversion from a high voltage storage battery to a low voltage storage battery or performing power conversion from the low voltage storage battery to the high voltage storage battery.
The DC-DC converter apparatus includes a high-voltage side switching circuit for converting a DC voltage having a high voltage into an AC voltage, a transformer for converting an AC high voltage into an AC low voltage, a low-voltage side rectifier circuit for converting a low voltage AC voltage into a DC voltage, and a control circuit for controlling the high-voltage side switching circuit and the low-voltage side rectifier circuit.
In the DC-DC converter apparatus, semiconductor elements forming the high-voltage side switching circuit and the low-voltage side rectifier circuit, the transformer, and the like generate heat. When a temperature is increased due to generation of heat, a loss is increased. Therefore, a container that houses electronic components forming the transformer and the circuits has a heat-radiating structure.
As the DC-DC converter apparatus, the following structure is known.
A circuit board is attached to a base plate made of metal. An opening is provided in a part of the circuit board, and a transformer is placed in the opening and is mounted on the base plate. A cover made of metal is combined with the base plate in which the circuit board and the transformer are housed. A protrusion portion protruding inward is provided in a top plate portion of the cover. The protrusion portion of the cover is brought into press-contact with the transformer, and the transformer is sandwiched between the base plate and the cover (for example, see PTL 1).